Nanopore device with improved sensitivity and method of fabricating the same

ABSTRACT

A nanopore device comprising a channel unit comprising a micro channel defined by a bottom surface and an insulator lateral wall; and a cover unit covering the micro channel, wherein the cover unit comprises a nanopore extending through the cover unit and connected to the micro channel; a first source/drain electrode disposed on an upper surface of the cover unit and adjacent to an inlet of the nanopore; an opening extending through the cover unit and connected to the micro channel; and a second source/drain electrode disposed on the upper surface of the cover unit and adjacent to the opening; as well as a method for fabricating and using the device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2012-0025664, filed on Mar. 13, 2012, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in theirentirety by reference.

BACKGROUND

A variety of methods for detecting target biomolecules such asdeoxyribonucleic acid (DNA) and DNA sequencing in a sample have beendeveloped. Among these methods, a nanopore method has been used inconjunction with a DNA detection system with high sensitivity. Ananopore DNA detection system detects DNA from a slight change inelectric current which occurs when DNA translocates through nanopores toperform DNA sequencing or to determine whether double-stranded orsingle-stranded DNA is present.

For example, a DNA detection system includes a nanopore formed through athin film including an insulating layer/conductive gate layer/insulatinglayer, upper and lower sample solution reservoirs that are formed insuch a manner that the nanopore is disposed therebetween, and source anddrain electrodes that are respectively put in the upper and lower samplesolution reservoirs. A sample solution of an electrolyte such as KCLincluding target biomolecules such as DNA may be filled in the upper andlower sample solution reservoirs and the nanopore.

In this structure, when a bias is applied to the conductive gate layer,target biomolecules exhibiting an electric charge in the sample solutionof an electrolyte may translocate through the nanopore. In this case,target biomolecules translocating through the nanopore may be identifiedor DNA sequencing may be performed by measuring an electric currentbetween the source and drain electrodes and measuring a turn-on gatevoltage applied to the conductive gate layer.

There is a need to perform more accurate measurements by increasing thesensitivity of conventional nanopore DNA detection systems. There isalso a need to increase measuring speed of conventional nanopore DNAdetection systems.

SUMMARY

Provided is a nanopore device that increases sensitivity by reducing adiameter of a nanopore or a thickness of a conductive gate layer, and amethod of fabricating the same.

Provided is a nanopore device by which an array including a plurality ofnanopores may be easily configured and in which a signal amplifyingcircuit is installed together, and a method of fabricating the nanoporedevice.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to an aspect of the present invention, a nanopore deviceincludes a channel unit including a micro channel defined by a bottomsurface and an insulator lateral wall; and a cover unit covering anupper portion of the micro channel, wherein the cover unit includes ananopore that is extending through the cover unit and connected to themicro channel; a first source/drain electrode that is formed on an uppersurface of the cover unit and adjacent to an inlet of the nanopore; anopening extending through the cover unit and connected to the microchannel; and a second source/drain electrode that is formed on the uppersurface of the cover unit so as to be adjacent to the opening.

In some embodiments, the cover unit may further include a gate electrodedisposed in the cover unit and surrounding the nanopore.

In some embodiments, the cover unit may further include a gateinsulating layer that covers the gate electrode on an internal wall ofthe nanopore.

In some embodiments, the nanopore device may further include a gatecontact plug extedning through the cover unit and electrically connectedto the gate electrode; and a contact unit disposed on an upper surfaceof the cover unit and electrically connected to the gate contact plug,the first source/drain electrode, and the second source/drain electrodethrough electrical wirings, respectively.

In some embodiments, the gate electrode may have a thickness of about0.3 nm to about 0.4 nm, and the nanopore may have an internal diameterof about 1 nm to about 1.5 nm at a portion where the gate electrode isdisposed.

In some embodiments, the cover unit may further include a first solutionreservoir that protrudes from the upper surface of the cover unit so asto surround the nanopore and the first source/drain electrode; and asecond solution reservoir that protrudes from the upper surface of thecover unit so as to surround the opening and the second source/drainelectrode.

In some embodiments, the first solution reservoir and second solutionreservoir may comprise a surface that is hydrophobic. For example, thefirst solution reservoir and the second solution reservoir may each beformed with a hydrophobic wall.

In some embodiments, the cover unit may include a plurality of firstsolution reservoirs.

In some embodiments, the cover unit may include a plurality of nanoporesand a plurality of first source/drain electrodes that are respectivelydisposed in the plurality of first solution reservoirs.

In some embodiments, the second solution reservoir may be disposedbetween the plurality of first solution reservoirs.

In some embodiments, the bottom surface of the microchannel may beformed of a semiconductor material.

In some embodiments, the nanopore device may further include at leastone column in the microchannel that is connected to the bottom surfaceof the microchannel and a lower (bottom) surface of the cover unit(i.e., extending between the cover unit and the bottom surface of themicrochannel) wherein the at least one column supports the cover unit,at least in part.

In some embodiments, the cover unit may be formed by stacking at leastone insulating layer. For example, the cover unit may include a firstinsulating layer, a second insulating layer formed on the firstinsulating layer, a third insulating layer formed on the secondinsulating layer, and a fourth insulating layer formed on the thirdinsulating layer. In this case, the third insulating layer may be formedof a different material from that of the second insulating layer and thethird insulating layer.

In some embodiments, the cover unit may include a gate electrode that isdisposed between the first insulating layer and the second insulatinglayer so as to surround the nanopore.

In some embodiments, the first source/drain electrode may have a ringshape so as to surround the inlet of the nanopore.

In some embodiments, to opening area of the opening may be greater thanan opening area of the nanopore.

According to another aspect of the present invention, a method offabricating a nanopore device includes sequentially stacking first,second, and third insulating layers on a semiconductor substrateincluding an active region and an insulator lateral wall surrounding theactive region; forming an opening and a plurality of first via holesthrough the first through third insulating layers so as to expose theactive region; forming a micro channel by etching a portion of theactive region, which is below the first insulating layer, through theopening and the plurality of first via holes; stacking a fourthinsulating layer on the third insulating layer; forming a nanoporethrough the first through fourth insulating layers so as to be connectedto the micro channel; and forming a first source/drain electrodeadjacent to an inlet of the nanopore and a second source/drain electrodeadjacent to the opening on the fourth insulating layer.

For example, a semiconductor substrate including the active region andthe insulator lateral wall may be formed by using a shallow trenchisolation (STI) process.

In some embodiments, the sequential stacking of first through thirdinsulating layers may include forming the first insulating layer on thesemiconductor substrate; partially forming a gate electrode on the firstinsulating layer; forming a second insulating layer on the firstinsulating layer on which the gate electrode is formed; forming thethird insulating layer having a different etch rate from the secondinsulating layer on the second insulating layer; forming a second viahole through the third insulating layer so as to face the gateelectrode; etching the second insulating layer so as to expose the gateelectrode through the second via hole; and filling a spacer in a spaceobtained by removing the second insulating layer.

In some embodiments, the gate electrode may be formed over an interfacebetween the active region and the insulator lateral wall.

In some embodiments, the thickness of the gate electrode may be about0.3 nm to about 0.4 nm.

In some embodiments, the first, second, and fourth insulating layers maybe formed of silicon oxide, and the third insulating layer may be formedof silicon nitride.

In some embodiments, the spacer may be formed of the same material asthe second insulating layer.

In some embodiments, the etching of the second insulating layer may use,for example, wet etching.

In some embodiments, the plurality of first via holes may be arrangedalong columns and rows at a regular interval, and a barrier having ahorizontal cross-sectional area that is greater than a size of eachfirst via hole may be formed between the plurality of first via holes.

In some embodiments, the forming of the micro channel may includewet-etching the active region in an under-cut manner so as to form atleast one column below the barrier disposed between the plurality offirst via holes.

In some embodiments, the forming of the nanopore may include forming amask layer on the fourth insulating layer and forming a mask pattern byetching the mask layer so as to remove a portion of the mask layercorresponding to the second via hole; exposing the second via hole byetching the fourth insulating layer through the mask pattern; forming ananopore by sequentially etching the spacer, the gate electrode, and thefirst insulating layer through the mask pattern and the second via hole;and removing the mask layer.

In some embodiments, the method may further include forming a gateinsulating layer so as to cover at least the gate electrode on aninternal wall of the nanopore.

In some embodiments, the gate insulating layer may be formed by using,for example, a thermal oxidation process.

In some embodiments, the internal diameter of the nanopore, which isreduced by the gate insulating layer, may be about 1 nm to about 1.5 nmat a portion where the gate electrode is disposed.

In some embodiments, the method may further include forming a gatecontact plug that is electrically connected to the gate electrode bysequentially etching the fourth insulating layer, the third insulatinglayer, and the second insulating layer.

Also provided is a method of analyzing a nucleic acid moleculecomprising contacting the nanopore of the nanopore device with a samplecomprising a nucleic acid (e.g., RNA or DNA), applying an electiccurrent between the first and second source/drain electrodes, anddetecting a change in the voltage between the first and secondsource/drain electrodes, or detecting a change in the voltage at thegate electrode. The relative magnitude of a change in the voltagebetween the first and second source/drain electrodes indicates therelative size of a base of the nucleic acid passing through thenanopore.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings of which:

FIG. 1 is a plan view of a nanopore device according to an embodiment ofthe present invention;

FIG. 2A is a cross-sectional view of the nanopore device taken along aline A-A′ of FIG. 1, according to an embodiment of the presentinvention;

FIG. 2B is a cross-sectional view of the nanopore device taken along aline B-B′ of FIG. 1, according to an embodiment of the presentinvention;

FIG. 3 is a simulation diagram showing a base sequence ofsingle-stranded deoxyribonucleic acid (DNA) being analyzed by using ananopore device, according to an embodiment of the present invention;

FIG. 4 is a graph showing characteristics whereby a voltage of a gateelectrode is changed according to the size of a base and a positionthrough which a base translocates when bases having different sizestranslocate through a nanopore;

FIG. 5 is a graph showing characteristics whereby a current betweensource/drain electrodes is changed according to the size of a base and aposition through which a base translocates when bases having differentsizes translocate through a nanopore;

FIG. 6 is a plan view of a nanopore device array according to anembodiment of the present invention; and

FIGS. 7 through 22 are diagrams for describing a method of fabricatingthe nanopore device of FIG. 1, according to an embodiment of the presentinvention.

DETAILED DESCRIPTION

Hereinafter, reference will now be made in detail to embodiments of ananopore device, and a method of fabricating the same, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, lengths andsizes of layers and regions may be exaggerated for clarity. As usedherein, the term “and/or” includes any and all combinations of one ormore of the associated listed items.

FIG. 1 is a plan view of a nanopore device according to an embodiment ofthe present invention. FIG. 2A is a cross-sectional view of the nanoporedevice taken along a line A-A′ of FIG. 1, according to an embodiment ofthe present invention. FIG. 2B is a cross-sectional view of the nanoporedevice taken along a line B-B′ of FIG. 1, according to an embodiment ofthe present invention.

Referring to FIGS. 1, 2A, and 2B, the nanopore device according to thepresent embodiment may include a channel unit 90 including a microchannel 11 that is surrounded and defined by a bottom surface 12 and aninsulator lateral wall 20 surrounding a perimeter of the micro channel11. The insulator lateral wall 20 joins the bottom surface 12 along alower periphery of the micro channel 11. The micro channel 11 has aspace with a predetermined length and width, and an insulator cover unit80 covering an upper portion of the micro channel 11. The cover unit maycontact with and join the insulator lateral wall 20 along an upperperiphery of the micro channel 11. The cover unit 80 may include ananopore 41 b that is perpendicularly formed through the cover unit 80and is connected to one end of the micro channel 11, a gate electrode 30formed in the cover unit 80 to surround the nanopore 41 b, a firstsource/drain electrode 62 that is formed on an upper surface of thecover unit 80 so as to be adjacent to an inlet 25 of the nanopore 41 b,an opening 45 that is perpendicularly formed through the cover unit 80and is connected to the other end of the micro channel 11, and a secondsource/drain electrode 64 that is formed on the upper surface of thecover unit 80 so as to be adjacent to the opening 45. The cover unit 80may further include a first solution reservoir 72 that is formed on theupper surface of the cover unit 80 so as to surround the nanopore 41 band the first source/drain electrode 62, and a second solution reservoir74 that protrudes on the upper surface of the cover unit 80 so as tosurround the opening 45 and the second source/drain electrode 64. Whenin use, an electrolyte solution (not shown) including a target material,for example, deoxyribonucleic acid (DNA), may be filled in and occupythe first solution reservoir 72, the second solution reservoir 74, thenanopore 41 b, the opening 45, and/or the micro channel 11.

The bottom surface 12 of the micro channel 11 may be formed of aninsulating material, or may be formed of a semiconductor material suchas silicon. When the bottom surface 12 is formed of a semiconductormaterial, the nanopore device may be easily formed by using a generalsemiconductor processing method. For example, the insulator lateral wall20 may be provided by an insulator material disposed on a semiconductorsubstrate, for instance, by forming an insulating layer around theperiphery of a semiconductor substrate by using a general shallow trenchisolation (STI) process. The cover unit 80 and the micro channel 11 maybe formed by providing additional insulator layers and etching a centralportion of the semiconductor substrate. A method of fabricating thenanopore device will be described below in more detail.

Referring to FIG. 2A, the nanopore device according to the presentembodiment may further include at least one column, that is, columns 14and 28 a that support the cover unit 80 in the micro channel 11. Thecolumns 14 and 28 a may be connected between an upper surface of thebottom surface 12 and a lower surface of the cover unit 80 and maysupport the cover unit 80 and the first and second solution reservoirs72 and 74 disposed on the upper surface of the cover unit 80. Thecolumns 14 and 28 a may be arranged at a regular interval, or may beirregularly arranged. The arrangement of columns may be selected so thattarget materials may easily translocate through the micro channel 11.

The cover unit 80 may be formed by sequentially stacking at least oneinsulating layer, for example, four insulating layers 22, 24, 26, and40. For example, the insulating layers 22, 24, 26, and 40 may includeoxide insulating layers 22, 24, and 26, and a nitride insulating layer40. By forming the cover unit 80 by using the insulating layers 22, 24,26, and 40, the nanopore 41 b may be formed as small as possible inconsideration of the size of an object (e.g., a single-stranded DNA) tobe identified, the micro channel 11 may be formed in the channel unit90, and the gate electrode 30 may be disposed in the cover unit 80. Thatis, the insulating layers 22, 24, 26, and 40 may be chosen inconsideration of a manufacturing process. Alternatively, a singleinsulating layer may constitute the cover unit 80.

The first source/drain electrode 62 that is formed on the upper surfaceof the cover unit 80 so as to be adjacent to the inlet 25 of thenanopore 41 b may have, for example, a ring shape so as to surround theinlet 25 of the nanopore 41 b. In general, when a single-stranded DNA isanalyzed, a negative voltage having the same polarity as DNA is appliedto the first source/drain electrode 62 and a positive voltage is appliedto the second source/drain electrode 64. Thus, when the firstsource/drain electrode 62 having a ring shape symmetrically surroundsthe inlet 25 of the nanopore 41 b, an electrical repulsive forcegenerated by the first source/drain electrode 62 may symmetrically acton bases of DNA translocating through the nanopore 41 b, therebyreducing sensing signal noise that is measured through the gateelectrode 30.

The opening 45 may guide target materials, which translocate to themicro channel 11 through the nanopore 41 b, to the second solutioncontainer 74. Thus, the opening 45 does not have to be minutely formedlike the nanopore 41 b, and a diameter of the opening 45 may be greaterthan a diameter of the nanopore 41 b. For example, a diameter of thenanopore 41 b may be about 1 nm to about 1.5 nm and a diameter of theopening 45 may be several mm.

The first and second solution reservoirs 72 and 74 for containing anelectrolyte solution including target materials may be formed on theupper surface of the cover unit 80 to each have a barrier rib or wall.In this case, a surface of the wall of each of the first and secondsolution reservoirs 72 and 74 may be processed to be hydrophobic so thattarget materials may not be attached thereto. For example, the first andsecond solution reservoirs 72 and 74 may comprise or be formed of aphotosensitive film or polydimethysiloxane (PDMS). However, thematerials and shapes of the first and second solution reservoirs 72 and74 are not particularly limited as long as the first and second solutionreservoirs 72 and 74 may contain an electrolyte solution.

The cover unit 80 may further include a gate insulating layer 28 that isformed to cover the gate electrode 30 on an internal wall of thenanopore 41 b. When the gate insulating layer 28 covering the gateelectrode 30 is formed on the internal wall of the nanopore 41 b, thenanopore device according to the present embodiment may operate as anionic field effect transistor (IFET). In addition, a gate contact plug66 that is perpendicularly formed through the cover unit 80 so as to beelectrically connected to the gate electrode 30 may be further formed onthe cover unit 80. One end of the gate contact plug 66 may contact thegate electrode 30 and the other end of the gate contact plug 66 may beexposed through the upper surface of the cover unit 80. However, thenanopore device does not have to operate as a transistor. For example,the nanopore device may operate by using only the first source/drainelectrode 62 and the second source/drain electrode 64 without the gateelectrode 30.

Contact units 65, 61, and 63 may be further formed on the upper surfaceof the cover unit 80 so as to be electrically connected to the gatecontact plug 66, the first source/drain electrode 62, and the secondsource/drain electrode 64 through wirings 60, respectively. Although notillustrated, signal amplifying circuits that are respectively connectedto the gate contact plug 66, the first source/drain electrode 62, andthe second source/drain electrode 64 so as to amplify measuring signalsmay be further formed on the upper surface of the cover unit 80.

The gate electrode 30 having conductivity may be formed of metal butalso may be formed of, for example, a silicon-based material (e.g.,polycrystalline silicon) doped with impurities. Since an intervalbetween bases of DNA is about 0.33 nm and a diameter of asingle-stranded DNA is about 1 nm, a thickness of the gate electrode 30may be about 0.3 nm to about 0.4 nm and an internal diameter of thenanopore 41 b may be about 1 nm to about 1.5 nm at a portion where thegate electrode 30 is disposed. The thickness of the gate electrode 30and the diameter of the nanopore 41 b may be restricted (small), therebypreventing two or more bases from translocating through the gateelectrode 30 simultaneously, and preventing two or more single-strandedDNA from translocating through the nanopore 41 b simultaneously.Accordingly, the nanopore device according to the present embodiment mayincrease measurement sensitivity for analyzing a base sequence of asingle-stranded DNA.

In the above-described nanopore device according to the presentembodiment, an electrolyte solution, for example, KCI may be filled inand occupy the first solution reservoir 72, the second solutionreservoir 74, the nanopore 41 b, the opening 45, and the micro channel11 and a sample containing a target material such as DNA may be furtheradded in the first solution reservoir 72. Then, when a negative voltageis applied to the first source/drain electrode 62, a positive voltage isapplied to the second source/drain electrode 64, and when a bias isapplied to the gate electrode 30, the nanopore 41 b enters a turn-onstate. In this case, a target material having negative polarity such asDNA may translocate from the first solution reservoir 72 to the microchannel 11 through the nanopore 41 b. While the target material istranslocating through the nanopore 41 b, a voltage of the gate electrode30 is changed or a current flowing between the first source/drainelectrode 62 and the second source/drain electrode 64 is changedaccording to the size of a base, and thus, a base sequence may bedetermined by measuring the change in the voltage or the current.

FIG. 3 is a simulation diagram showing a base sequence ofsingle-stranded DNA being analyzed by using a nanopore device, accordingto an embodiment of the present invention. In FIG. 3, for convenience ofdescription, only the insulating layers 22 and 24 around the gateelectrode 30 and the nanopore 41 b are schematically shown. In addition,in FIG. 3, bases that are positioned at five different positions in thenanopore 41 b are shown for the purposes of illustration.

FIG. 4 is a graph showing changes in the voltage measured at the gateelectrode is changed as a nucleic acid translocates through a nanopore.The change in voltage reflects the size of a base and its position inthe nanopore. In FIG. 4, {circle around (1)} through {circle around (5)}corresponds to positions of the bases shown in FIG. 3. Referring to FIG.4, as the size of a base is increased, a voltage of the gate electrode30 is changed more when the base translocates through the nanopore 41 b.

FIG. 5 is a graph showing changes in current between the first andsecond source/drain electrodes 62 and 64 as a nucleic acid translocatesthrough a nanopore. The current changes according to the size of a baseand the position in the nanopore. Referring to FIG. 5, as the size of abase is increased, the current is changed more when the basetranslocates through the nanopore 41 b. Accordingly, the nanopore deviceaccording to the present embodiment may detect a change in voltage orcurrent to accurately analyze a base sequence of DNA. In particular, asdescribed above, the thickness of the gate electrode 30 and the diameterof the nanopore 41 b may be restricted so as to reduce measurementnoise, thereby increasing accuracy.

According to the present embodiment, since the first and second solutionreservoirs 72 and 74 are horizontally formed on the upper surface of thecover unit 80, convenience of use is ensured. As described below, aplurality of first solution reservoirs are disposed around the secondsolution reservoir 74, and thus, a nanopore device array may be easilyembodied. FIG. 6 is a plan view of a nanopore device array according toan embodiment of the present invention.

Referring to FIG. 6, in the nanopore device array according to thepresent embodiment, two or more first solution reservoirs, that is,first solution reservoirs 72 a and 72 b may share the micro channel 11with each other and may be connected to each other around the secondsolution reservoir 74. Nanopores 41 b may be respectively disposed tocorrespond to the first solution reservoirs 72 a and 72 b. In FIG. 6,for convenience of description, nanopore inlets 25 a and 25 b are shownto respectively correspond to the first solution reservoirs 72 a and 72b. In addition, a first source/drain electrode 62 a and 62 b, gatecontact plugs 66 a and 66 b, and contact units 61 a, 61 b, 63 a, 63 b,65 a, and 65 b may be formed on the cover unit 80 to respectivelycorrespond to the nanopore inlets 25 a and 25 b. The remaining portionsof the nanopore device array shown in FIG. 6 are the same as in thenanopore device described with reference to FIGS. 1, 2A, and 2B, andthus, the details thereof will be omitted.

In this structure, when a negative voltage is applied to the firstsource/drain electrode 62 a and 62 b and a positive voltage is appliedto the second source/drain electrode 64, target materials contained inthe first solution reservoirs 72 a and 72 b may translocate through thenanopore 41 b and then may be collected in the second solution reservoir74 through the micro channel 11. According to the present embodiment, alarge amount of samples may be simultaneously analyzed by using aplurality of solution containers, that is, the first solution containers72 a and 72 b.

Hereinafter, a method of fabricating the nanopore device shown in FIG. 1will be described with reference to FIGS. 7 through 22. Referencenumerals that are not described with reference to FIG. 1 through 6 willbe described with reference to FIGS. 7 through 22. In each of FIGS. 7through 22, (a) is a plan view and (b) is a cross-sectional view takenalong a line A-A′.

Referring to FIG. 7, an insulator lateral wall 20 is formed around anedge portion of a semiconductor substrate. For example, the insulatorlateral wall 20 may be formed by forming a trench in the edge portion ofthe semiconductor substrate by using a general STI process and fillingan insulating layer in the trench. For example, the insulator lateralwall 20 may comprise any suitable insulator material, such as SiO₂.Then, an active region 10 that will be processed in a subsequent processmay remain on a central portion of the semiconductor substrate. In thiscase, the semiconductor substrate may be, for example, a bulk siliconsubstrate or a silicon-on-insulator (SOI) substrate.

Then, as shown in FIG. 8, the first insulating layer 22 is formed on anentire upper surface of the semiconductor substrate, contacting theactive central region of the semiconductor and the insulator lateralwall region, and then the gate electrode 30 is partially formed on thefirst insulating layer 22. In this case, the gate electrode 30 may beformed over an interface between the active region 10 and the insulatorlateral wall 20. In other words, the gate electrode is positioned on aregion of the first insulating layer that overlaps the interface betweenthe active region and the insulator lateral wall. The first insulatinglayer 22 may be formed of a silicon oxide, for example, SiO₂. The gateelectrode 30 may be formed of metal or a silicon-based material (e.g.,poly silicon) doped with impurities. When the nanopore device is used toanalyze a base sequence of DNA, since an interval between bases is about0.33 nm, a thickness of the gate electrode 30 may be about 0.3 nm toabout 0.4 nm. According to the present embodiment, since the nanoporedevice is manufactured by using a general semiconductor process, thegate electrode 30 may be formed to have a small thickness. In addition,for example, the gate electrode 30 may be formed of a thin electrodematerial such as graphene.

Then, referring to FIGS. 9 and 10, the second insulating layer 24 andthe third insulating layer 40 are sequentially stacked on the firstinsulating layer 22 on which the gate electrode 30 is formed. The secondinsulating layer 24 may be formed as the same oxide layer as the firstinsulating layer 22. However, since the third insulating layer 40 servesas a mask in an etch process with respect to the first and secondinsulating layers 22 and 24 that will be described below, the thirdinsulating layer 40 may be formed of an insulating material having adifferent etch rate from the first and second insulating layers 22 and24. For example, the third insulating layer 40 may be formed of siliconnitride (SiNx) such as Si₃N₄.

Then, as shown in FIG. 11, a second via hole 41 is formed through thethird insulating layer 40. The second via hole 41 may be formed to facethe active region 10 and the gate electrode 30. In other words, thesecond via hole 41 is positioned in a region of the third insulatinglayer that overlaps the gate electrode and the active central region ofthe semiconductor substrate. When the second via hole 41 is formed, thesecond insulating layer 24 may be partially etched.

As shown in FIG. 12, an etchant is provided through the second via hole41 so as to wet-etch the second insulating layer 24. Then, the gateelectrode 30 may be exposed through a portion 21 that is removed byetching the second insulating layer 24. The wet etching is performeduntil the gate electrode 30 is at least partially exposed. When the gateelectrode 30 is exposed, a spacer 42 is formed by filling the samematerial as the third insulating layer 40 in the portion 21 that isremoved by etching the second insulating layer 24, as shown in FIG. 13.

Then, referring to FIG. 14, a plurality of first via holes 43 and theopening 45 are formed through the first through third insulating layers22, 24, and 40. In this case, the first via holes 43 and the opening 45are formed in a region corresponding to the active region 10, except fora region corresponding to the gate electrode 30, so as to expose theactive region 10. The first via holes 43 may be spaced apart from eachother along columns and rows by a predetermined interval. In this case,at least one barrier or barriers 49 may be regularly or irregularlyarranged between the first via holes 43 and may each have a horizontalcross-sectional area that is at least three times or more greater thanthe size of each of the first via holes 43. The barriers 49 may beunetched portions of the third insulating layer 40 while forming thefirst via holes 43 through the third insulating layer 40. The barriers49 serve as a mask so that a portion of the active region 10corresponding to the barriers 49 remains after a subsequent process offorming the micro channel 11 by etching the active region 10. Theportion of the active region 10, which remains in the micro channel 11,may function as a column for supporting the cover unit 80. In FIG. 14, aratio between the size of the first via holes 43 and the size of thebarriers 49 is just an example. In reality, the size of the barriers 49may be much greater than the size of the first via holes 43. The opening45 may be formed on the active region 10 to be opposite to the gateelectrode 30. For example, an opening area of the opening 45 may be atleast two times or more greater than an opening area of the nanopore 41b that will be formed later.

Then, referring to FIG. 15, an etchant may be provided through the firstvia holes 43 and the opening 45 to wet-etch the active region 10. Then,a portion of the active region 10, which is below the first insulatinglayer 22, may be etched and removed to form the micro channel 11 havinga predetermined space below the first insulating layer 22. The wetetching is performed for a predetermined period of time according to thethickness of the active region 10 so that the bottom surface 12 mayremain below the active region 10. In addition, the wet etching isperformed in an under-cut manner so that the active region 10 maypartially remain below the barriers 49 disposed between the first viaholes 43 to form at least one column 14. The micro channel 11 may alsobe formed by isotropic dry etching instead of wet etching.

Then, as shown in FIG. 16, the fourth insulating layer 26 may be formedto a predetermined thickness on an entire upper surface of the thirdinsulating layer 40. Then, the second via hole 41 and the first viaholes 43 may be covered and/or filled (completely or partially) with thefourth insulating layer 26. In order to fill the second via hole 41 andthe first via holes 43, the fourth insulating layer 26 may be formed byusing, for example, a sputtering method. The fourth insulating layer 26may be formed of the same oxide material as the first insulating layer22. When the fourth insulating layer 26 is formed, a material 26 a ofthe fourth insulating layer 26 may partially remain on the bottomsurface 12.

Then, referring to FIG. 17, a mask pattern 51 is formed by stacking amask layer 50 on the fourth insulating layer 26 and etching the masklayer 50 so as to remove a portion of the mask layer 50 corresponding tothe second via hole 41. Then, as shown in FIG. 18, the fourth insulatinglayer 26 may be etched through the mask pattern 51 so as to expose thesecond via hole 41. For example, the fourth insulating layer 26 may bewet-etched. Then, a portion of the fourth insulating layer 26 may beremoved above the second via hole 41 to form a predetermined space 23.

Then, as shown in FIG. 19, the spacer 42, the gate electrode 30, and thefirst insulating layer 22 may be sequentially etched through the maskpattern 51 and the second via hole 41 to form a nanopore 41 a. In thiscase, the spacer 42, the gate electrode 30, and the first insulatinglayer 22 may be etched by anisotropic dry etching. After the nanopore 41a is formed, the mask layer 50 is removed, as shown in FIG. 20.

Then, as shown in FIG. 21, the gate insulating layer 28 is formed on aninternal wall of the nanopore 41 a. The gate insulating layer 28 may beformed to cover at least the exposed portion of the gate electrode 30.Thus, the nanopore device according to the present embodiment mayoperate as an IFET. In addition, by forming the gate insulating layer28, a final nanopore 41 b may have a reduced internal diameter. Since adiameter of a single-stranded DNA is about 1 nm, the final nanopore 41 bmay be formed to have a diameter of about 1 nm to about 1.5 nm. To thisend, a process condition for forming the gate insulating layer 28 may beappropriately controlled. For example, the gate insulating layer 28 maybe formed by using a thermal oxidation process. In this regard, thediameter of the final nanopore 41 b may be controlled by controlling theduration of the processing period. When the gate insulating layer 28 isformed by using the thermal oxidation process, an oxidation layer may beformed in a portion of the micro channel 11, through which silicon isexposed. For example, an oxidation layer 28 a may be formed on a surfaceof the bottom surface 12 and the oxidation layer 28 a may also be formedon surfaces of the columns 14.

Lastly, referring to FIG. 22, the fourth insulating layer 26, the thirdinsulating layer 40, and the second insulating layer 24 are sequentiallyetched so as to expose a portion of the gate electrode 30 to form acontact hole. Then, the first source/drain electrode 62, the secondsource/drain electrode 64, the gate contact plug 66, and wirings 60 maybe formed on the fourth insulating layer 26. In this case, an electrodematerial 67 may also be partially deposited on the bottom surface 12through the opening 45. Although not illustrated, signal amplifyingcircuits that are respectively connected to the gate contact plug 66,the first source/drain electrode 62, and the second source/drainelectrode 64 so as to amplify measuring signals may be further formed onthe fourth insulating layer 26.

As shown in FIGS. 1, 2A, and 2B, the first solution reservoir 72 and thesecond solution reservoir 74 may be further formed on the fourthinsulating layer 26. The first solution reservoir 72 may be formed tosurround the nanopore 41 b and the first source/drain electrode 62. Thesecond solution reservoir 74 may be formed to surround the opening 45and the second source/drain electrode 64. As described above, the firstand second solution reservoirs 72 and 74 may each be formed with ahydrophobic wall. For example, the first and second solution reservoirs72 and 74 may be formed of a photosensitive layer orpolydimethylsiloxane (PDMS) and then adhered onto the fourth insulatinglayer 26.

Since the above-described method of fabricating a nanopore device uses asemiconductor process, a diameter of the nanopore 41 b and a thicknessof the gate electrode 30 may be minimized. For example, the gateelectrode 30 having a small thickness may be formed by using a metaldeposition process or a growth process of polysilicon. The diameter ofthe nanopore 41 b may be reduced by forming the gate insulating layer 28by using a thermal oxidation process. Since the nanopore device isformed on a semiconductor substrate, a signal amplifying circuit may beformed to be integrated with the nanopore device. In addition, a typicalsemiconductor process is used, and thus the nanopore device may beeasily manufactured. Since the nanopore device includes two solutionreservoirs 72 and 74 that are horizontally disposed on the cover unit80, the nanopore device may be easily manufactured and used. Forexample, since the first source/drain electrode 62, the secondsource/drain electrode 64, the gate contact plug 66, and the wirings 60are disposed on the upper surface of the cover unit 80, a complexmanufacturing process is not required and all manipulations may beperformed on the upper surface of the cover unit 80 during use of thenanopore device. In addition, a nanopore device array may be formedusing similar techniques.

As described above, according to the one or more of the aboveembodiments of the present invention, examples are explained anddrawings are described in order to help in the understanding of ananopore device and a method of fabricating the same. However, it shouldbe understood that the exemplary embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

What is claimed is:
 1. A nanopore device comprising: a channel unitcomprising a micro channel defined by a bottom surface and an insulatorlateral wall; and a cover unit covering the micro channel, wherein thecover unit comprises: a nanopore extending through the cover unit andconnected to the micro channel; a first source/drain electrode disposedon an upper surface of the cover unit and adjacent to an inlet of thenanopore; an opening extending through the cover unit and connected tothe micro channel; a second source/drain electrode disposed on the uppersurface of the cover unit and adjacent to the opening; and a gateelectrode that surrounds the nanopore.
 2. The nanopore device of claim1, wherein the cover unit further comprises a gate insulating layer thatcovers the gate electrode on an internal wall of the nanopore.
 3. Thenanopore device of claim 1, further comprising: a gate contact plugextending through the cover unit and electrically connected to the gateelectrode; and a contact unit disposed on the upper surface of the coverunit and electrically connected to the gate contact plug, the firstsource/drain electrode, and the second source/drain electrode throughelectrical wiring.
 4. The nanopore device of claim 1, wherein thicknessof the gate electrode is about 0.3 nm to about 0.4 nm, and an internaldiameter of the nanopore is about 1 nm to about 1.5 nm in an area wherethe gate electrode is disposed.
 5. The nanopore device of claim 1,wherein the cover unit further comprises: a first solution reservoirthat protrudes from the upper surface of the cover unit and surroundsthe nanopore and the first source/drain electrode; and a second solutionreservoir that protrudes from the upper surface of the cover unit andsurrounds the opening and the second source/drain electrode.
 6. Thenanopore device of claim 5, wherein the first solution reservoir and thesecond solution reservoir are each comprise a hydrophobic wall.
 7. Thenanopore device of claim 5, wherein the cover unit comprises a pluralityof first solution reservoirs.
 8. The nanopore device of claim 7, whereinthe cover unit comprises a plurality of nanopores and a plurality offirst source/drain electrodes that are respectively disposed in theplurality of first solution reservoirs.
 9. The nanopore device of claim7, wherein the second solution reservoir is disposed between theplurality of first solution reservoirs.
 10. The nanopore device of claim1, wherein the bottom surface comprises a semiconductor material. 11.The nanopore device of claim 1, wherein the cover unit comprises a stackhaving at least one insulating layer.
 12. The nanopore device of claim1, wherein an opening area of the opening is greater than an openingarea of the nanopore.
 13. A method of analyzing a nucleic acid moleculecomprising contacting the nanopore of the device of claim 1 with asample comprising a nucleic acid, applying an electric current betweenthe first and second source/drain electrodes, and detecting a change inthe voltage between the first and second source/drain electrodes. 14.The method of claim 13, wherein the relative magnitude of a change inthe voltage between the first and second source/drain electrodesindicates the relative size of a base of the nucleic acid passingthrough the nanopore.
 15. A method of analyzing a nucleic acid moleculecomprising contacting the nanopore of the device of claim 1 with asample comprising a nucleic acid, applying an electric current betweenthe first and second source/drain electrodes, and detecting a change involtage at the gate electrode.
 16. A nanopore device comprising: achannel unit comprising a micro channel defined by a bottom surface andan insulator lateral wall; and a cover unit covering the micro channel,wherein the cover unit comprises: a nanopore extending through the coverunit and connected to the micro channel; a first source/drain electrodedisposed on an upper surface of the cover unit and adjacent to an inletof the nanopore; an opening extending through the cover unit andconnected to the micro channel; a second source/drain electrode disposedon the upper surface of the cover unit and adjacent to the opening; andat least one column connected between an upper surface of the bottomsurface and a lower surface of the cover unit in the micro channel andsupporting the cover unit.
 17. A nanopore device comprising: a channelunit comprising a micro channel defined by a bottom surface and aninsulator lateral wall; and a cover unit covering the micro channel,wherein the cover unit comprises: a nanopore extending through the coverunit and connected to the micro channel; a first source/drain electrodedisposed on an upper surface of the cover unit and adjacent to an inletof the nanopore; an opening extending through the cover unit andconnected to the micro channel; and a second source/drain electrodedisposed on the upper surface of the cover unit and adjacent to theopening; wherein the first source/drain electrode has a ring shape andsurrounds the inlet of the nanopore.